Sleep mask



FIG. 1 is a perspective front view of a sleep mask embodying the new design in position of use;

FIG. 2 is a rear elevation view thereof, but shown in an open position;

FIG. 3 is a front elevation thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is another perspective view thereof, but shown with broken line subject matter.

The broken lines in FIG. 2 illustrate portions of the sleep mask. The broken lines in FIG. 8 illustrate environment. None of the broken lines form part of the claimed design. 

CLAIM We claim the ornamental design for a sleep mask, as shown and described. 